Cancer is a generic term for a large group of diseases that can affect any part of the body. There are over one hundred different types of such diseases and other common terms used to describe them include malignant tumours and neoplasms.
One defining feature of cancer is uncontrollable growth of cells that lead to the rapid creation of abnormal cells. Cells are the building blocks of the body. These cells do not die as normal cells do but instead continue to grow beyond their usual boundaries and as such can then invade adjoining parts of the body and spread to other tissues and organs. This process is referred to as metastasis, that is, cancerous cells spreading beyond where they initially developed. Metastases are the major cause of death from cancer.
Image Credit: National Cancer Institute
Each cancer is classified by the type of cell that is initially affected, for example, if it found to have initially formed in the prostate, it will be called prostate cancer, regardless of where it metastasized to.
Image Credit: National Cancer Institute
Cells become cancerous due to DNA (DeoxyriboNucleic Acid) damage. DNA is a ubiquitous material in cells. It contains all the information needed for cell and ultimately body function and it is used to direct all the actions within a cell. When DNA gets damaged in a normal cell, the cell either repairs the damage or it dies. However, in cancer cells, the damaged DNA is not repaired, and the cell doesn’t die. It goes on making new cells that contain the same abnormal DNA as the first cell does, and in most cases, these abnormal cells have no use to the body.
There are 6 hallmarks of a cancer cell. They include sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis (Cell144, March 4, 2011).
In most cases, the abnormal cells continue to multiply and grow until they form an mass of tissue called a tumour. Some, cancers, however, like leukemia, rarely form tumors. Instead, these cancer cells involve the blood and blood-forming organs and circulate through other tissues where they grow.
Tumors are a classic sign of inflammation, and can be benign (non-cancerous) or malignant (cancerous).
Benign tumors can cause problems as they can grow very large and press on healthy organs and tissues. However, they cannot grow into or invade other tissues. This inability means they cannot spread to other parts of the body (metastasize) and as such these tumors are almost never life threatening.
Determining what causes cancer is complex. Many factors are known to contribute to the risk of cancer these include largely environmental factors and to a lesser degree genetics. Age is another risk factor that has been linked to development of cancer.
Risk factors that promote cancer
When cancer begins it invariably produces no symptoms. Signs and symptoms gradually appear as the mass continues to grow or ulcerates. The signs and symptoms will depend on where the cancer is, how big it is, and how much it affects the organs or tissues. If a cancer has spread (metastasized), signs or symptoms may appear in different parts of the body.
Only a few symptoms are specific to any cancer type. There are, however, a number of general symptoms of cancer but having these symptoms do not necessarily mean that one has cancer; these symptoms could be as a result of some other disease or ailment.
Local symptoms may occur due to the mass of the tumor or its ulceration.
Occur due to distant effects of the cancer that are not related to direct or metastatic spread.
- Darker looking skin (hyperpigmentation)
- Yellowish skin and eyes (jaundice)
- Reddened skin (erythema)
- Itching (pruritis)
- Excessive hair growth
Symptoms of Metastasis
Due to the spread of cancer to other locations in the body.
For further reading and research into the causes, nature and risk factors of Cancers, you may visit the links below, among others.